Gridlocks – did you unlock the grid?
pH 2
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pH values can be calculated from [H ] and conversely [H ] can be calculated from pH values using the
equations below. But before you dive for your calculator it is worth knowing how reasonably convenient
numbers convert so you get a ‘feel’ for the type of answer you are expecting. Before you answer the
gridlocks below fill in the table of pH values – see how many you can do without using the calculator. All pHs
here to 1 d.p. (log 2 ≈ 0.3 and log 5 ≈ 0.7).
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pH = −log10[H ]
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−pH
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[H ] = 10
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[H ]
pH
2
−0.3
2  10
0.5
0.3
5  10
0.2
0.7
2  10
4.3
5  10
−5
5  10
[H ]
pH
−7
6.7
−8
7.3
−12
11.7
−15
14.3
Problem Solving Gridlock 1
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Each row, column and 2 x 2 box contains information about the first four [H ] listed above. Use your problem
solving skills and the answers in the table above to fill in the blank boxes.
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[H ]
2
pH
0.5
−5
5  10
0.2
0.3
0.7
4.3
−0.3
pH
0.7
4.3
−0.3
0.3
−5
5  10
2
0.5
0.2
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[H ]
Gridlocks – did you unlock the grid?
Gridlock 2
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[H ]
pH
−8
2  10
−12
−15
2  10
5  10
−7
5  10
14.3
6.7
7.3
11.7
−12
5  10
−7
5  10
6.7
7.3
2  10
11.7
14.3
2  10
−15
−8
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pH
[H ]
Gridlock 3
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[H ]
−4
5  10
pH
0.05
−13
−10
12.7
9.7
3.3
2  10
2  10
1.3
1.3
3.3
2  10
9.7
12.7
5  10
pH
−10
−13
2  10
−4
0.05
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[H ]